SAN DIEGO, July 3 (Reuters) - Residents of a Southern California town confronted their mayor on Wednesday over the arrival of Central American migrants for processing after they slipped across the Mexico border into Texas, extending an influx that has swamped authorities there.

Families and unaccompanied minors have been fleeing strife-torn Guatemala, El Salvador and Honduras and streaming by the thousands over the U.S.-Mexico frontier with the help of human smuggling rings.

Most have shown up in Texas, swamping detention and reception centers there and leading U.S. immigration authorities to set up overflow sites in California and other states in the Southwest to help screen and manage the influx.

Dozens more migrants were shipped to California for processing on Wednesday, a day after protesters blocked buses full of Central American families bound for a Border Patrol station north of San Diego.

Later on Wednesday at least 1,000 residents of Murrieta near San Diego crammed into a town hall meeting to protest over hundreds of migrants the federal government aims to provisionally accommodate in the San Diego suburb.

Protesters on Tuesday had blocked three buses carrying the first group of 140 migrants headed to Murrieta, forcing the caravan to turn around and head to another Border Patrol station in San Diego for processing there instead.

U.S. Homeland Security Secretary Jeh Johnson, in an interview with MSNBC, said he found television images of that demonstration "very disturbing" to watch.

"Because of the recent influx of kids and families crossing the border in the Rio Grande sector, our processing capability (there) is full and we've had to go to other places in the Southwest simply to process these people," Johnson said.

"So when someone interrupts the ability of the border patrol to process a migrant, you're preventing us from conducting basic health screening and the basic background checks on who these people are," he said.

'SEND WASHINGTON A BILL'

Immigration officials said most of the families headed for California were likely to be released under limited supervision to await deportation. Many would to be placed with relatives or friends or in temporary housing provided by charity groups.

On Wednesday, border protection officials confirmed that a separate group of undocumented migrant families with children were sent to a processing center in El Centro, California, a desert community about 100 miles (160 km) east of San Diego.

Immigration and Customs Enforcement agency spokeswoman Virginia Kice said authorities were being especially careful to avoid disclosing the whereabouts of the detainees "so that mobs can't go down and root out those people".

At the town hall meeting in Murrieta, Mayor Alan Long told the angry throng that he had been advised by U.S. officials to expect another group of about 140 immigrants every three days for several weeks.

He blamed federal officials for the influx, saying that he intended to "send Washington a big fat bill" for expenses.

Residents filled the meeting hall to capacity and spilled out into a parking lot, carrying signs with slogans like "Illegals today, Jihadists with Nukes tomorrow!!".

A man scuffled with police after they stopped him walking into the meeting draped with a flag. The meeting adjourned at about 11 p.m. local time and residents left without incident. (Writing and additional reporting from Los Angeles by Steve Gorman and Dan Whitcomb, and from Seattle by Eric M. Johnson; Editing by Mark Heinrich)